Except they never do, because they don't know PHP on Windows either and are afraid of breaking things, and the customer ends up with a PHP/Wordpress installation that is 4 years out of date. Luckily, most of those are internal-only apps, but it still sucks.
Where I used to work, we developed and supported a SaaS app based on PHP with PostgreSQL and Apache. We had two self-hosting customers who ran on Windows Server with SQL Server for the exact reasons mentioned, and they were our most troublesome customers. Performance tuning (and hence regular complaints that 'our' app was horribly slow) was a particular issue - mostly due to their admins' lack of relevant experience on both the stack...and Windows Server(!). The whole setup was a pain because we got so much flak, despite the premise of 'self-hosting' being that the customer had sufficient smarts to support the infrastructure and stack and we'd just support the functional and development aspects of the app.
One customer also had the system so locked down that for remote admin we had to connect to a jump box via VPN + RDP and then jump from that to the server with another RDP connection. Fetching large log files through that setup was a challenge.
Partly for our sanity, we persuaded one customer to let us migrate them to a Linux server; that went very well and really cut down on angst all round even though we then took responsibility for platform support.
In my limited experience, this is the sales team saying 'anything' to get the sale.